HISTORICAL SHORELINE CHANGES IN BEACHES LOCATED AT THE MUNICIPALITIES OF SAN JUAN AND CAROLINA, PUERTO RICO (1936-2010)

This research includes a study of historical shoreline changes in beaches located in the municipalities of San Juan and Carolina from 1936 to 2010. The beaches included in this study are El Escambrón, Ocean Park, Balneario de Carolina, and Piñones beaches. Remote Sensing, Geographic Information Systems (GIS), field work, and evaluation of data already published by local and federal agencies are used in order to determine the geomorphic dynamic of the beaches. Vertical aerial photographs in a scale of 1:20,000 are used to define the extension of the subaerial beach, beach width and shoreline position by period. The Arc View 10.1 software was used to build the different layers of information containing beach geomorphic variables for each period. These data are compared to identify if there is erosion, accretion, or no change in the morphology of each study site. Possible causes of shoreline changes as occurrence of tropical cyclonic systems and man-made activities were evaluated in this study. Preliminary results indicate that there are important shoreline changes in the extension and area in subaerial beaches during the ‘60s, with a decrease on the beach loss from the decade of ‘70s- ‘80s. These data coincide with data published by Barreto and Morelock. The beach loss in the ‘60s could be related to the occurrence of tropical cyclonic systems in the area during that period. This type of data is important to develop databases that support the design of coastal management plans for the coastal zone of the Island.